1. Field of the Invention
The invention relates to improvements in nozzle constructions for coating machines and the like. More specifically the invention relates to a fluid nozzle having improved means for supplying the fluid to the nozzle discharge opening and to a mechanism for adjusting and maintaining the size of the nozzle opening at the adjusted position.
2. Description of the Prior Art
Gaseous fluid nozzles have been used in the coating industry for at least two basic functions, the first of which may be classified as "doctoring means," wherein the nozzle jet of fluid, usually gaseous fluid such as air, acts directly on a liquid or semi-liquid material which has been applied as a coating to the surface of a substrate, such as paper, film, foil, cloth or metal strip, in excess immediately ahead of or upstream from the particular nozzle in terms of movement of the substrate relative to the nozzle to reduce the coating to the desired thickness and smoothness.
Another basic use of gaseous fluid nozzles in the strip processing industry is as a "backing means," in which case, the air or other gaseous fluid jet is applied to one side of the moving strip, such as paper or plastic film, to maintain a uniform pressure against an object on the opposite side, such as a cooling roll or a rigid coating knife. One example of this "backing means" use is illustrated in U.S. Pat. No. 3,113,884.
It is not intended to limit the principles of the present invention to the paper coating industry or the coating of substrates of this general type, but rather it is fully contemplated that the principles of the present invention may be applied to nozzles for many uses, some of which may not be presently known.
It also is important that the nozzle opening be uniform within close limits throughout the entire length of the nozzle opening to insure a uniform coating on the moving substrate throughout its width. This can be a problem in many fluid nozzles due to the transverse length of the nozzle opening. Variations in the nozzle opening cause variations in the force output of the jet which produces variations in the coating thickness left on the strip.
It is extremely important in the coating industry that downtime and scrap be kept to a minimum. Since the coating station is usually only one part of a complicated expensive machine with a high rate of production, such as a paper board machine, or a steel galvanizing line, faults such as dirt in the nozzle produce scrap rapidly while stops disrupt many processes and restarting may take many minutes. Since a speck of dirt on or in the nozzle can cause a streak in a 200 inch wide strip running 1000 feet per minute or more, lost time and lost production cannot be tolerated.
With the improved opening style nozzle of this invention, dirt and streak problems can be corrected in seconds if dirt is loose, or may be slightly longer if scrubbing is required, and when the nozzle is restored to service, all settings and adjustments remain unchanged from the previous condition.
These problems have long been recognized and U.S. Pat. Nos. 2,766,720 and 2,981,223 were offered to allow one nozzle subassembly to be quickly substituted for another. However, although these and variations thereon worked, it proved extremely difficult to adjust the two subassemblies to produce the same result, defeating the intended purpose.
In an effort to meet this problem, an opening style nozzle was developed such as shown in U.S. Pat. No. 3,314,163. While many such nozzles have been built and are in use around the world, the clamping means for clamping the nozzle halves together has certain faults, particularly in nozzles having a relatively long length for wide strips. Specifically, the stops which set the nozzle discharge opening are spaced generally at the ends of the nozzle body, while the points at which clamping pressure is applied are spaced between them. This system distorts the nozzle body halves and the lips attached to them, which cause variations in the nozzle discharge opening. These variations depend upon the relation between the force created by the internal pressure of the coating fluid and the clamping pressure, and are therefore difficult to control. The present invention is believed to overcome most of the problems with the type of nozzle construction shown in U.S. Pat. No. 3,314,163.
Another important feature of any coating control nozzle is the means by which the coating control fluid is supplied to the nozzle lips which form the discharge opening. Heretofore, the coating control fluid was supplied by various supply pipes and manifold arrangements for discharge into distribution chambers adjacent the nozzle openings. U.S. Pat. Nos. 2,766,720 and 3,141,194 show a type of fluid supply wherein the fluid is fed to the nozzle discharge opening through the center or axis of a rotatable nozzle.